Japanese Patent Laid-Open No. 8-105384 discloses a conventional variable displacement swash plate type compressor (hereinafter, described as a compressor). In the compressor, a housing is formed by a front housing, a cylinder block and a rear housing. In the front housing and the rear housing, suction chambers and discharge chambers are respectively formed. Further, in the rear housing, a control pressure chamber is formed.
In the cylinder block, a swash plate chamber, a plurality of cylinder bores and a center bore are formed. The center bore is formed at a rear side of the cylinder block.
A drive shaft is inserted through the housing, and is rotatably supported in the housing. In the swash plate chamber, a swash plate that is rotatable by rotation of the drive shaft is provided. Between the drive shaft and the swash plate, a link mechanism that allows change of an inclination angle of the swash plate is provided. Here, the inclination angle refers to an angle which the swash plate forms with respect to a direction orthogonal to a rotational axis of the drive shaft.
Further, in the respective cylinder bores, pistons are respectively accommodated to be able to reciprocate, and compression chambers are respectively formed in the respective cylinder bores. A conversion mechanism causes the respective pistons to reciprocate in the cylinder bores at a stroke corresponding to the inclination angle, by rotation of the swash plate. Further, an actuator can change the inclination angle, and a control mechanism controls the actuator.
The actuator has a first movable body, a second movable body, a thrust bearing and the above described control pressure chamber. The first movable body is disposed in the center bore, and is movable in a rotational axis direction in the center bore. In the first movable body, a shaft hole through which a rear end portion of the drive shaft is inserted is formed. Thereby, the rear end portion of the drive shaft is rotatable in the shaft hole of the first movable body. The second movable body has the drive shaft inserted therethough. The second movable body is disposed forward of the first movable body, and is movable in the rotational axis direction. The thrust bearing is provided between the first movable body and the second movable body.
The control mechanism regulates the pressure of a refrigerant in the control pressure chamber by performing communication control of the control pressure chamber and the discharge chamber, besides performing communication control of the control pressure chamber and the suction chamber. Further, the control mechanism has an O-ring and a pair of searing rings. The O-ring and the respective sealing rings are located between an outer circumferential surface of the first movable body and an inner circumferential surface of the center bore. The respective sealing rings are disposed at a front end side and a rear end side of the first movable body with the O-ring therebetween. By the O-ring and the respective sealing rings, a space between the control pressure chamber and the swash plate chamber is sealed.
In this compressor, the control mechanism regulates the pressure of the refrigerant in the control pressure chamber, whereby the first and the second movable bodies and the thrust bearing can be moved in the rotational axis direction. Thereby, in this compressor, the link mechanism allows change of the inclination angle of the swash plate, and a discharge capacity per one rotation of the drive shaft is changeable.
In the above described conventional compressor, at a time of changing the discharge capacity, the control mechanism regulates the pressure of the refrigerant in the control pressure chamber by each communication control of the suction chamber and the discharge chamber, and the control pressure chamber while sealing the space between the control pressure chamber and the swash plate chamber. Therefore, in this compressor, work and means for preventing leakage of the refrigerant from the control pressure chamber are needed, and manufacture cost increases.
The present invention is made in the light of the above described conventional situation, and a problem to be solved by the invention is to provide a variable displacement swash plate type compressor capable of realizing reduction in manufacture cost in a compressor that changes a discharge capacity by using an actuator.